Gut microbiota is known to have a role in shaping key aspects of postnatal life, such as the development of the immune system (Mazmanian et al., (2005) Cell 122(1): 107-118; Peterson et al., (2007) Cell Host Microbe 2(5): 328-339), and influencing the host's physiology, including energy balance. Transplanting the gut microbiota from normal mice into germ-free recipients increased their body fat without any increase in food consumption, raising the possibility that the composition of the microbial community in the gut affects the amount of energy extracted from the diet (Backhed et al., (2004) Proc Natl Acad Sci USA 101(44): 15718-15723). There is at least one type of obesity-associated gut microbiome characterised by higher relative abundance of Firmicutes or a higher Firmicutes to Bacteroidetes ratio (Ley et al., (2005) Proc Natl Acad Sci USA 102(31): 11070-11075; Turnbaugh et al., (2006) Nature 444(7122): 1027-1031). The role of intestinal microbiota in disease has also been shown. Gut microbes serve their host by functioning as a key interface with the environment; for example, they can protect the host organism from pathogens that cause infectious diarrhea. A decreased diversity of fecal microbiota and specifically a reduced diversity of Firmicutes in Crohn disease patients has been reported (Manichanh et al., (2006) Gut 55(2): 205-211), while it was recently shown that Faecalibacterium prausnitzii displays anti-inflammatory action and can potentially be used for the treatment of this disease (Sokol et al., (2008) Proc Natl Acad Sci USA 105(43): 16731-16736).
Efficient growth of pre-weaned dairy calves together with low incidence of disease (especially diarrhea and pneumonia) are prerequisites for their optimal performance after weaning and contribute in the profitability of a dairy enterprise. For every 1 kg of pre-weaning average daily gain, milk yield increased by 1,113 kg in the first lactation (Soberon et al., (2012) J Dairy Sci 95(2): 783-793). The notion that calves' intestinal microbiota profiles are probably related with growth and disease already exists. Probiotics, bacteria with a beneficial effect on animals' intestinal health, have been found to have antidiarrheal capacities and enhance growth rates in calves (Donovan et al., (2002) J Dairy Sci 85(4): 947-950; Timmerman et al., (2005) J Dairy Sci 88(6): 2154-2165).
However, methods for preventing diarrhea and improving growth of newborn animals are still needed.